Peroxisome Subpopulations of the Rat Liver: Isolation by Immune Free Flow ElectrophoresisAlfred Völkla, Heribert Mohra, and H. Dariush Fahimiaa Department of Anatomy and Cell Biology II, University of Heidelberg, Heidelberg, Germany Correspondence to: Alfred Völkl, Dept. of Anatomy and Cell Biology II, U. of Heidelberg, Im Neuenheimer Feld 307, 69120 Heidelberg, Germany.
Peroxisomes (POs) are a heterogenous population of cell organelles which, in mammals, are most abundant in liver and kidney. Although they are usually isolated by differential and density gradient centrifugation, isolation is hampered by their high fragility, sensitivity to mechanical stress, and their sedimentation characteristics, which are close to those of other major organelles, particularly microsomes. Consequently, until now only the so-called "heavy" POs with a buoyant density of 1.221.24 g/cm3 have been highly purified from rat liver, whereas the other subpopulations also present in that tissue have escaped adequate characterization. The purification of these subpopulations has become an essential task in view of the functional significance of POs in humans, and the putative importance of peroxisomal subpopulations in the biogenesis of this organelle. Here we used an alternative novel approach to density gradient centrifugation, called immune free flow electrophoresis (IFFE). IFFE combines the advantages of electrophoretic separation with the high selectivity of an immune reaction. It makes use of the fact that the electrophoretic mobility of a subcellular particle complexed to an antibody against the cytoplasmic domain of one of its integral membrane proteins is greatly diminished, provided that the pH of the electrophoresis buffer is adjusted to pH ~8.0, the pI of IgG molecules. Because of this reduced electrophoretic mobility, IgG-coupled particles can be separated in an electric field from those that are noncoupled and hence more mobile. The IFFE technique has been recently applied for isolation of regular POs ( (J Histochem Cytochem 47:11111117, 1999) Key Words: isolation, peroxisome subpopulations, immune free flow electrophoresis
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